Most of the implantable electromedical devices (IMDs) that have practical significance are intended to emit electrical pulses to excitable bodily tissue via suitably placed electrodes. Furthermore, many devices can measure electrical pulses and stimuli in the body of the patient in a targeted manner and record or evaluate these electrical pulses and stimuli over a relatively long period of time in order to select an individualized treatment and perform an in vivo check of the success of the treatment.
In order to carry out these functions, electronic/electrical functional units for generating and measuring the pulses and for suitably controlling the pulse generation are accommodated in the housing of the device, and electrodes or connections for at least one electrode lead, in the distal end section of which the electrodes for transmitting pulses to the tissue are accommodated, are provided directly on the outside of the device. The electronic/electrical functional units in the interior of the housing are intended to be connected to the outer electrodes or electrode lead connectors in a manner that ensures functionality that is absolutely and permanently reliable under the special conditions of the implanted state.
This task is performed by so-called feedthroughs, which are the subject of numerous and highly diverse developments. The task of a feedthrough is that of routing the electrical signals through the hermetically sealed housing and, thereby, enabling electrical contact to be established between the electronics in the hermetically sealed housing and the electrodes in the body of the patient. Terminal pins are used for this purpose in many such feedthroughs, which are contacted in the housing interior to the printed circuit board or a similar conductor support that is located there and route the signals through the housing.
In conjunction with the trend toward miniaturization and the advances made in electronics, rapid transformations have taken place in soft soldering technology (solder) in recent years. Manual assembly processes were increasingly replaced by fully automated pick-and-place machines, and through-hole technology (THT) was gradually replaced by surface-mount technology (SMT). This makes it possible to design smaller, more compact circuits and, therefore, also incrementally results in smaller, more patient-compatible IMDs. In order to achieve the numerous advantages of SMT, feedthroughs must meet the requirements placed on a surface-mount device (SMD). To this end, in particular, the pin that is used, which is usually soldered-in (e.g., brazed) in a high-temperature process, must meet high electrical, thermal, and mechanical requirements before it can be soldered onto the printed circuit board or conductor support. The reliability of all joints of the feedthrough must be ensured over the entire lifespan, also under the influence of bodily fluids.
For this reason, there are terminal pins that are made entirely of a noble metal (such as, for example, platinum, platinum-iridium, palladium), which can be easily and reliably connected to the conductor support in a soft soldering process, although the high price thereof is disadvantageous. Moreover, there are multi-component arrangements comprising, for example, the actual terminal pin and a soft-solderable additional component (e.g., pad, barrel) made of different materials.
The latter solutions require a separate assembly and production step. Components are provided, which are joined with the feedthrough after or during the high-temperature soldering (e.g., brazing). The additional assembly outlay is not inconsiderable. It can cause the production costs for the additional components to exceed the material value thereof by several-fold. The additional components are usually very small and delicate (typically <1 mm) and, therefore, are difficult to place and orient. Furthermore, separate production tools are required to install the additional components. Before assembly, the components must be additionally stored and tested, and they require additional lot management and tracking.
The additional joining process may result in rejects. If the process of joining the pin with components is carried out integrally with the joining process of the feedthrough, an additional screening inspection must be carried out, in which the process of the pin joining is assessed. After the joining, the connection point must be inspected for adhesion, sufficient stability, and service life. It is entirely possible that the components of the pin can tilt and become displaced, resulting in displacement when placed on the printed circuit board. This must be detected in a separate test step and must be avoided and tested in the feedthrough assembly.
U.S. Pat. No. 7,340,305 discloses a feedthrough of an IMD, in which terminal pins are used that have a core that is not based on expensive platinum, platinum-iridium, or palladium and that have a single- or multi-component, conductive coating. The coating makes it possible, on the one hand, to control and/or limit oxidation of the terminal pin under the conditions in which an implanted device is used, and, on the other hand, to connect the terminal pin to a printed circuit board by means of a soft-soldering process. United States Publication No. 2011/0303458 also discloses terminal pins having a partially multi-layer design and the use thereof in feedthroughs of IMDs.
U.S. Pat. No. 7,747,321 discloses, as shown in FIG. 1 thereof, a cardiac pacemaker 1 having a pacemaker housing 3 and a header 5, in the interior of which other electronic components, as well as a printed circuit board (PCB) 7, are disposed, wherein an electrode lead 9 is connected to the (non-illustrated) lead terminal of said cardiac pacemaker, said lead terminal being disposed in the header. A feedthrough 11 provided between the device housing 3 and the header 5 comprises a plurality of terminal pins 13. The terminal pins are inserted, at one end, through a corresponding via in the printed circuit board and are soft-soldered therewith. Said terminal pins have a wire core, which is made of tantalum, niobium, titanium, molybdenum, or copper, for example, and an oxidation-resistant sheathing made of a biocompatible material, such as gold, platinum, titanium, or the like.
The present invention is directed toward overcoming one or more of the above-mentioned problems.